P881: DURABILITY OF RESPONSES WITH BIWEEKLY DOSING OF TECLISTAMAB IN PATIENTS WITH RELAPSED/REFRACTORY MULTIPLE MYELOMA ACHIEVING A CLINICAL RESPONSE IN THE MAJESTEC-1 STUDY
Authors: Manisha Bhutani, Alfred Garfall, Katarina Uttervall, Saad Z Usmani, Lionel Karlin, Lotfi Benboubker, Hareth Nahi, Jesús San Miguel, Danielle Trancucci, Keqin Qi, Tara Stephenson, Alfredo Perales-Puchalt, Katherine Chastain, Ajai Chari
Journal: HemaSphere (2023)

Topic: 14. Myeloma and other monoclonal gammopathies - Clinical Background: Teclistamab is the first B-cell maturation antigen (BCMA) bispecific antibody approved for the treatment of relapsed/refractory multiple myeloma (RRMM) at a dose of 1.5 mg/kg weekly (QW) given subcutaneously. A less frequent dosing schedule offers added convenience and flexibility to patients, physicians, and caregivers. Aims: To evaluate the ability of patients to maintain their responses after transitioning from QW to every other week (Q2W) dosing schedules in the pivotal phase 1/2 MajesTEC-1 trial (NCT03145181/NCT04557098). Methods: Eligible patients had RRMM and received ≥3 prior lines of therapy including a proteasome inhibitor, immunomodulatory drug, and anti-CD38 antibody. Prior BCMA-targeted therapy was not allowed in this cohort. All patients provided informed consent. Patients received the recommended phase 2 dose (RP2D) of 1.5 mg/kg teclistamab QW, with the option to switch to Q2W dosing if patients achieved a confirmed partial response or better after ≥4 cycles of treatment (phase 1) or a confirmed complete response (CR) or better for ≥6 months (phase 2). Response was assessed per IMWG 2016 criteria. Results: As of Dec 9, 2022, 165 patients in the pivotal cohort had received teclistamab at the RP2D. Of 104 responders, 60 patients switched to Q2W dosing; 50 met the protocol-defined criteria for switching, and 10 switched who did not meet the criteria (4 due to adverse events [AEs]; 6 due to other reasons). Patients who switched had a median age of 64 years, 58% were male, 25% had high-risk cytogenetics, 7% had extramedullary plasmacytomas, and 3% had International Staging System stage III disease at baseline. Patients received a median of 4 prior lines of therapy, and 75% were triple-class refractory. At the time of switch, 49 (82%) patients achieved ≥CR, and 11 (18%) had a very good partial response. Median time to switch from QW to Q2W dosing was 11.1 months (range, 3–20). At median 11.1-month (range, 2–24) follow-up since switching, the median duration of response from the date of switch was 20.5 months (range, 1–23), with 40/60 patients still in response and ongoing treatment. Of the remaining patients, 13/60 have progressed (median time from switch to progression not estimable), 2 discontinued due to AEs, 1 discontinued for other reason, and 4 died. Additional results will be presented. Summary/Conclusion: Overall, patients from the MajesTEC-1 study who transitioned from QW to less frequent Q2W dosing of teclistamab had sustained remission, with a median duration of response of 20.5 months from the date of switch. © 2023 American Society of Clinical Oncology, Inc. Reused with permission. This abstract was accepted and previously presented at the 2023 ASCO Annual Meeting. All rights reserved. Keywords: Phase I/II, B-cell maturation antigen, Bispecific, Multiple myeloma